Is Late-Night Eating Bad for You?

You might want to forget that late-night snack. Recent research shows chronic late-night eating could wreak havoc on your health.

In an ongoing study that compared eating earlier in the day and later eating, researchers found the latter can lead to increased weight and higher insulin and cholesterol levels. Regularly throwing down late at night also affected fat metabolism negatively and found markers that implicated heart disease, diabetes and other health issues.

“We know from our sleep loss studies that when you’re sleep deprived, it negatively affects weight and metabolism in part due to late-night eating, but now these early findings, which control for sleep, give a more comprehensive picture of the benefits of eating earlier in the day,” said Namni Goel, a research associate professor of psychology in psychiatry in the division of sleep and chronobiology at the Perelman School of Medicine at the University of Pennsylvania, and lead author of the study. “Eating later can promote a negative profile of weight, energy and hormone markers—such as higher glucose and insulin, which are implicated in diabetes, and cholesterol and triglycerides, which are linked with cardiovascular problems and other health conditions.”

In the study, participants ate during the daytime eating (three meals and two snacks between 8 a.m. and 7 p.m.) for eight weeks, had a two-week break and then ate late (three meals and two snacks from noon to 11 p.m.) for eight weeks. They slept between 11 p.m. and 9 a.m. for the entire study period.

Researchers found that during daytime eating, the hormone ghrelin, which stimulates appetite, peaked earlier in the day, while leptin, which helps folks feel full, peaked later, suggesting the participants received cues to eat earlier, and eating earlier likely helped them stay satiated longer. This suggests eating earlier may help prevent overeating in the evening and at night.

“These findings suggest that eating earlier in the day may be worth the effort to help prevent these detrimental chronic health effects,” said Kelly Allison, associate professor of psychology in psychiatry and director of the Center for Weight and Eating Disorders, and senior author of the study. “We have an extensive knowledge of how overeating affects health and body weight, but now we have a better understanding of how our body processes foods at different times of day over a long period of time.”

Earlier studies like this one have suggested similar results, but this is the first long-term study looking at the timing of eating patterns that also controlled for sleep-wake cycles, exercise and nutrient intake to look at the effects of prolonged eating at different times of day.